This invention relates to the protection of telecommunications lines from transient voltage surges, such as those due to lightning, and, more particularly, to an assembly for providing such protection to a plurality of transmission line-pairs carried by a multi-conductor cable.
Telecommunications transmission lines are typically susceptible to lightning strikes when not within a building. Accordingly, primary lightning protection is usually provided where the transmission lines enter a building. However, modern telecommunications equipment, such as computer controlled private branch exchanges, are very sensitive to transient surges such as those caused by lightning strikes and the primary lightning protection is often inadequate. Telecommunications equipment manufacturers therefore commonly provide secondary surge protection within their equipment. Such equipment, for example, a computer controlled private branch exchange, may have twenty, fifty or even more, telephone line-pairs connected thereto. Therefore, if the secondary surge protection is incorporated within the equipment, this leads to a number of disadvantages. One disadvantage is that the secondary surge protection takes up valuable "real estate" within the telecommunications equipment. Another disadvantage is that bulky cables carrying thick wire have to be utilized between the primary protection and the secondary protection. It is therefore a primary object of the present invention to provide transient voltage surge protection circuitry for telecommunications equipment which overcomes the aforementioned disadvantages.